Projection micro-stercolithography (PμSL) is a recently-developed technology that allows additive manufacture of three-dimensional structures in nearly any configuration, with precise control over feature size. For instance, formation of a structure characterized by features with a horizontal and/or vertical resolution on the order of several hundred nanometers to several hundred microns. Typically, a curable resin is placed in a reservoir, and the resin is selectively cured, e.g. via directing a laser or other light source to selectively expose portions of the resin, causing precursor materials in the resin to form a solid structure in the exposed regions, typically via a polymerization process.
The exposure may be performed in a layer-wise fashion, and one or more two-dimensional masks may be employed to facilitate the selective exposure. Accordingly, each layer may be formed using a different mask, and the three-dimensional structure may be formed by exposing a layer using a two-dimensional mask, moving a stage along a third dimension (e.g. depth) into the reservoir, and exposing another layer using the same or a different two-dimensional mask to form a new layer on top of the previously formed layer. The thickness of each layer depends upon the properties of the resin (e.g. the depth to which light exposure may penetrate and effectively cause precursors to transform) and the magnitude of the stage movement between layers. In various approaches, each layer may have a thickness in a range from about 500 nm to about 500 μm.
While PμSL conveys extremely advantageous control over the structural arrangement of the fabricated part, structures produced using PμSL are limited in that the precursor materials must include photo-reactive components that will transform into a corresponding solid part upon exposure to the light source. To date, PμSL is limited to photopolymer resins that are curable in the UV range. Accordingly, while PμSL provides remarkable control over the structure of the fabricated part, the compositions which may be used to accomplish such structures are very limited in scope. Moreover, conventional compositions are limited to a single material, i.e. the final structure consists of a single material.
Some applications have included post-processing to modify or functionalize the structures produced by PμSL, e.g. by plating the printed structure with a material of interest. However, these post-processing techniques only coat the surfaces of the printed structure, and add thickness to the structure. Accordingly, the bulk of the structure cannot include the materials of interest, and it is not possible to precisely control which surfaces of the structure are coated. Moreover, adding such materials to the surface of the structure disadvantageously reduces the resolution of features.
In applications where small feature size is important (e.g. formation of micro lattices, capillary structures, etc.) these limitations are a significant disadvantage, and in some cases prohibit the modification or functionalization of the structures altogether. Even where not prohibitive to modification or functionalization as a whole, a lack of precise control over the spatial distribution of the modification or functionalization prohibits the manufacture of customized components particularly suited for individual purposes for which conventionally-manufactured components are unsuitable.
Similar limitations have been encountered using other additive manufacturing techniques such as deposition modeling, continuous liquid interface production and binder printing.
Accordingly, it would be highly beneficial to provide materials and techniques for forming structures via PμSL and other additive manufacturing techniques that may include a broader range of compositions beyond photopolymer resins that are curable in the UV range to expand the applicability of PμSL and other additive manufacturing techniques to a wide range of fields and tasks.